In the relevant technical field, there is a known way of producing lenses for spectacles intended to incorporate solely the appropriate optical properties to enable the user to have correct vision, the lenses being designed either as corrective lenses or as protective lenses (such as lenses of sunglasses).
In this field, the development of the technology for manufacturing lenses, particularly lenses of plastic material produced by injection moulding or casting processes, has given rise to the need to incorporate more complex structures into lenses to provide additional functions, other than those solely designed to provide correct vision. It is therefore desirable to combine the optical benefits or properties with purely decorative or functional aspects, designed for example to improve the interfacing of the lens with the main or auxiliary components of the mounting frames. At the same time, there is a need to simplify any additional machining of a lens to achieve the various decorative effects or the various functions that can be obtained in the lens.